The massive economic growth in China has come at a very visible environmental cost, as Beijing and other major Chinese cities are now plagued with air pollution. The problem has led the new Chinese premier to declare war on smog—and the government has enlisted drones in the fight.

The state-run China Daily recently reported that the Ministry of Environmental Protection has started to deploy surveillance drones to search for illegal polluters. Deputy Minister of Environmental Protection Zhai Qing announced that drones are now surveying the areas surrounding Beijing and the neighboring provinces of Hebei and Shanxi for sources of air pollution. The drones, which cover 70 square kilometers (about 30 square miles) in each flight, have already led to over 200 actions against polluters, according to Zhai.

The ministry has employed four small drones so far, but it will not expand the drone fleet because of “a shortage of flight controllers,” according to a report by the South China Morning Post. The drones have helped catch industrial polluters who have evaded regulators in the past by shutting down operations.

“It was difficult for the central government’s law enforcers to collect evidence when they make inspection trips outside of Beijing because locals easily recognize them, and polluting factories swiftly suspend production, leaving few traces,” ministry spokesperson Yang Yipeng told the Morning Post.

The drones can identify lawbreakers by the color of smoke coming out of smokestacks. “The drones also captured pictures of flames in the open air, and that is still only the tip of the iceberg,” Yang said. Ironically, the progress of drone operations has been impeded because they have not been allowed to operate in airspace below 1,000 meters (about 3,300 feet)—which means that their view is often diminished by smog.

China is also experimenting with the use of drones to clear smog. A parachute-winged drone has been used in tests to spray a catalyst to dissipate smog during air pollution emergencies.